Print-wheel mechanism



Feb. 20, 1951 J. A. CALDWELL PRINT WHEEL MECHANISM 2 Shoots-Sheet 1 Original Filed June 20, 1942' INVENTOR. JOHN A. CALDWELL vl ih.

ATTORNEY Pmma Feb. 20, 1951 John A. Caldwell, Philadelphia, Pa., assignor, by

'mesne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Original application. June 20, 1942, Serial No.

Divided and this application October 24, 1946, Serial No. 705,301

6 Claims. (CL 3461Q6) The present application is a division of my copending application Serial Number 447,863, filed on June 20, 1942, now Patent 2,423,480, issued July 8, 1947. That application is directed generally to the features of a self-balancing potentiometer of the strip chart type, while the present application is specifically directed to the print wheel carriage and the mechanism by means of which the print wheel and the ink wheel are rotated. I

In most multiple recording instruments there is provided a print wheel carriage on which is formed a plurality of printing characters. Each of these characters must be moved to a recording position corresponding to the value of the condition under measurement when a particular primary element, for example a thermocouple, is connected to the instrument. Thereafter the print wheel is moved to bring the character then in recording. position into engagement with a chart to make a record. There is also provided an ink wheel having one or more ink pads that are brought into engagement with the printing characters prior to the time each record is made. If all the records are to be in the same color a single ink pad may be used. It is more usual, however, to have each record made in a different color so that adifferent ink pad must This means that the movement of the ink wheel must be provided for each printing character.

rotated in such a manner that they will not get out of step.

It is a. further object'of the invention to pro vide a novel and accurate construction of a print wheel carriage by means of which the print wheel and ink wheel may be rotated as the print wheel is moved away from and toward the chart.

mechanism as a whole.

In this fashion immediately after a record has z which arrangement is entirely mounted on the carriage.

It is a further object of the invention to provide a novel means for holding the ink wheel in position on a print wheel carriage. This means is so arranged that the ink wheel can be mounted in only one position, and is further characterized by the fact that the ink wheel may be moved into place on the print wheel carriage without engaging the printing characters of the print wheel.

The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advan-- tages and specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which is illustrated and described a preferred embodiment of the invention.

In the drawings:

Figure 1 is a top view, partly in section, of the potentiometer instrument,

Figure 2 is a side view looking from the right in Figure 1 of the print wheel carriage,

Figure 3 is a sectional view of a portion of the print wheel carriage,

Figure 4 is a view taken on line 4-4 of Figure 2,

Figure 5 is a line taken on line 5-5 of Figure 4,

and

Figure 6 is a view taken on line 6-6 of Figure 2.

The above mentioned Patent 2,423,480 has in it a complete disclosure of the potentiometer Reference is made to that application for a description of various details of the instrument which are not pertinent to the subject matter of the present case.

As is well known, potentiometer mechanisms are used to measure accurately various conditions such as temperature. For this purpose thermocouples are subjected to the temperature to be measured and the E. M. F. produced by these thermocouples is impressed in sequence upon the potentiometer network of the instrument. A print wheel carriage is then moved to a position above a recording chart corresponding to the temperature to which the thermocouple'then connected with the instrument is subjected. A record is then made of this temperature and a different thermocouple is connected to the instrument and the print wheel carriage is moved to a position corresponding to this temperature.

The mechanism by which this is done is described in detail in the above mentioned parent patent and for purposes of this disclosure it is necessary to refer only briefly to various parts of the mechanism shown in Figure 1 to describe how this operation is performed.

In response to potentiometer unbalance a reversible motor is operated in one direction or the other to shift a cable 00, which is mechanically attached to the motor, in one direction or the other. This cable, as shown in Figure l of the drawings, passes around a series of pulleys I45 to I48 inclusive on a frame 12 and is attached at its ends to a print wheel carriage 90 at a point 9|. As the motor is energized this cable pulls the print wheel carriage in one direction or the other to a position above the recording chart 2I9. When the potentiometer circuit is balanced the driving motor will be deenergized and the print wheel carriage will be in the proper position. Deenergization and therefore non-movement of the print wheel carriage is detected by a detecting mechanism including a part GI which is engaged by a cam I59. Upon stoppage of the print wheel carriage this detecting mechanism acts through suitable driving means to move a lever I which is pivoted at I10, first upwardly then downwardly and then upwardly again to accomplish the printing and indexing operations. The specific manner in which this is done is immaterial as far as the subject matter of this case is concerned since the present case is directed specifically to the construction of the print wheel mechanism. It is sufficient to say that a channel member I05 shown in Figures 1', 2 and 3 is attached to lever I14 and is therefore first moved upwardly in Figure 2 a sufficient distance to bring the print wheel into engagement with the chart. This channel member is then moved downwardly to a predetermined point and then returned to the position shown in Figure 2 of the drawing.

-While the downwardly and return movements are taking place the ink and print wheel are rotated to bring a new printing character into recording position above the chart.

- It is noted that the print wheel carriage 90 carries upon its upper surface a pair of contacts which engage respectively a slidewire I6 and a collector bar I8. These parts are mounted upon an insulating support 83 that extends lengthwise of the instrument and which is held in position thereon. The position of the contacts 20 along the slidewire determines the balance point of the potentiometer mechanism and therefore the position of the print wheel carriage. Therefore, as the motor rotates, the print wheel carriage will be moved back and forth across the instrument and carry the contact 20 with it across the slidewire to a position of balance. This print wheel carriage has on it a print wheel 92 that is provided with printing characters or numerals 99 which are to be moved into engagement with the chart when the print wheel carriage reaches a balanced position. It Is noted that chart II! is moved under the print wheel at a constant speed by a chart drum I. The manner In which the print wheel carriage operates will now be described.

Refer now to Figures 2 to 6 which show the print wheel carriage In detail. The print wheel carriage 90 is supported at its front end by a roller 94 that is received in a channel member 90 which runs the length of the instrument and is attached at its ends to the frame members "A and 12B of frame I2. The rear end of the print 4 wheel carriage is supported by means of rollers 06, 91, and which bear against and roll on a shaft 99 which is also attached at its ends to the frame parts "A and 123. The rollers 90 and 01 are rigidly mounted on the print wheel carriage, and the roller 98 is supported on a spring I00 which is attached to the print wheel carriage. In this manner, the roller 90 is forced into engagement with the rod 99 to prevent any upward movement between the print wheel carriage and the shaft, and to keep the print wheel carriage rigidly mounted in position as it moves back and forth above the chart 2I9, upon which the recording of the temperature is to be made. The print wheel carriage 90 has formed on one side thereof, a downwardly extending plate IOI which has a stud shaft I02 rigidly mounted therein. Pivoted on'this shaft is a supporting plate member I03 that has a roller I00 journaled on its rear end. This roller rides in a channel member I00 that is moved in a manner described above, for the purpose of producing the printing operation, and for the purpose of actuating a switch to connect the instrument to different thermocouples.

As more particularly shown in Figure 4, the shaft L2 has a sleeve I06 rotatably mounted on it. This sleeve, along with a second sleeve I09. that is rotatable on the first, are both held in position on the shaft I02 by means of a suitable lock washer I01. The plate I03 is staked to the sleeve I06 so that the plate and sleeve can oscillate around the shaft. The sleeve I00 has a gear I09 and a ratchet wheel IIO staked to it. The ratchet wheel serves the purpose of rotating the ink'pad assembly which is mounted on the former sleeves. The ink pad assembly is made of tubular moulding III that may be of plastic or metal and which is formed with a series of radially extending fins IIIA that serve to divide this moulding into a series of compartments. The axial bore of the moulding has a circular flange with a sloping face or surface II2, formed on its right-hand side, which engages with a cooperating surface II! on a flange member Ill that Is suitably fastened to the sleeve I08. This member is provided with a pin II5 that cooperates with a groove H0 formed in a central opening III in the flange of the moulding III. The central opening III in the flange is eccentric in shape as shown best in Figure 5. The ink pad assembly is held on sleeve I08 by means of a knob IIQ that has a cam face II9 engaging the left end pf the moulding and which serves to properly center the assembly. Located within. the radially extending compartments of the moulding III are felt pads I20, each of which may be impregnated with a different color ink if desired, so that each of the records made of the differentthermocouple temperatures will be recorded in a distinctive color. The felt pads are held in place in the moulding by means of a shield III as best shown in Figure 4.

The ink pad assembly is mounted on the print wheel carriage by moving the moulding III containing the pads on the sleeve I00 from the left in Figure 4. Since the printing characters 90 normally engage the ink pads I20 some means must be provided for keeping these parts separated while the ink pads are being moved into place. This is the reason why the central opening III is made eccentric in shape. As a first step in assembling the moulding III bearing the ink pads I20 upon the print wheel carriage 00, the channel member Ill is operated so as to rotate the print wheel "as well as the sleeve I (on which the ink pad assembly is mounted) until a selected printin character or numeral 93 is aligned with the pointer I26. When the parts are in such an alignment, the pin II5 on the flange member I I4 is at its furthest point of travel away from the print wheel 92 or about 90 in a clock-wise direction from the position in which it is shown in Fig. 2. With the pin H5 as far as possible away from print wheel 92, the ink pad assembly can be rotated about pin III as a pivot to separate the ink pads I from the printing characters 93. In mounting the moulding on the sleeve I06, the moulding is first rotated in the air about its own central axis until its groove H6 is lined up with pin H5, and moved toward the right in Figure 4. The moulding is then moved clockwise from the axial position in Figure 5 around pin II5 as a center (counterclockwise in Figure 2) to separate the felts I20 and the printing characters 93. Thereafter the moulding is again moved to the right in Figure 4 until its surface II2 engages surface I I3. Knob H9 is then screwed into place; engagement between its surface II9 forcing surfaces H2 and H3 into engagement with each other. Thus the moulding is rotated back into an axial position and centered by the concentric surfaces H3 and I I9 with the ink pads in engagement with the printing characters on the print wheel.

Also mounted on the plate I03 is a stud shaft I22. This shaft has rotating upon it, a sleeve I23 that is held in place by means of a washer I24. Staked to the sleeve is a drive gear I25. Also mounted on the sleeve I23 is the print wheel 92 that is held in proper position relative to the sleeve by means of engagement between a slot in the print wheel, and a pin I26 extending from the sleeve. Before the print wheel is placed on the sleeve, an indicating drum I21 is moved into place as shown best in Figure 6. This drum has a series of numbers on it which correspond to the print characters 93 on the print wheel, and are so displaced with respect to these characters, that when a printing character is in engagement with the chart, the corresponding numeral on this drum will be in a position where it can be seen from the front of the instrument as shown best in Figure 2. A pointer I26 is attached to the plate I03, and cooperates with the drum I21 to indicate the proper number. The print wheel and the indicating drum are held in place on the sleeve I23 by means of a knob I29 that is screwed on the outer end of the sleeve. As best shown in Figure 3, the gear I09 serves to drive the gear I by means of idler pinions I 30. both of which are mounted for rotation on the plate I03.

Since it is imperative that the print wheel can be exactly located with respect to the print wheel carriage a spring I3I is placed between the plate IOI of the print wheel carriage and the oscillating plate I03. This'spring serves to take up any slack in the parts, and always keeps the plate I03 properly placed, with respect to the plate IOI. For a similar reason, a spring I32 is inserted between the plate I03 and the gear I25 in order that the print wheel will be properly located on its shaft I22.

The print wheel carriage 96 is also provided on its front end, with an indicating pointer I34 that coperates with a scale I35, which is attached to the channel member 95 and extends across the front of the instrument. This indicator serves the purpose of showing the value of the temperature being measured as it moved in front of the scale I35.

The print wheel and the ink pads are normally kept from rotating on their shafts by means of a pawl I36 that is pivoted at I31 on the oscillating plate I03, and which is biased into engagement with teeth on the ratchet wheel IIO by means of a spring I33. A roller I39 which extends from the pawl I36 engages a surface of arm I40 on a second pawl III that is pivoted at I42 on the carriage plate IOI. This pawl is normally biased in a counter-clockwise direction in Figure 3, by means of a spring I43 that is equal'in strength to the spring I33. This latter pawl is used to rotate the print wheel to bring a new printing character into printing position above the chart each time a new thermocouple is connected to the instrument. The operation takes place due to an oscillation of plate I03 which is imparted thereto by means of the channel member I05. This channel member is moved in an arc concentric with the stud shaft I02, by means of a mechanism mentioned above, after the instrument has reached a balanced position.

In the operation of the print wheel, as the channel I05 is moved upwardly, the member I03 will be moved in a counter-clockwise direction in Figure 2 or a clockwise direction in Figure 3 to bring a printing character 93 into engagement with chart 2I9 that is placed over chart driving drum I44.

After a printing character has been brought into engagement with the chart, channel I05 will be moved downwardly. This means that the member I03 will be moved counter-clockwise in Figure 3 with the pawl I36 in engagement with ratchet IIO thus preventing any relative rotation of the parts mounted on member I03. As this movement continues the roller I39 on pawl I36 will move to the right along the surface of arm I40 until 'such time as the lever arm between roller I39 and the pivot I42 for pawl I4I has been shortened enough for the force of spring I43 to overcome that of spring I33. At that time the pawl I will move into engagement with the ratchet H0 and, acting through the arm I40, will move pawl I36 out of engagement with the ratchet. This will occur at the bottom of the stroke of lever I14, and with the printing wheel in its highest position above the chart drum. Lever I14 will then be moved to move channel I05 upwardly, which means that member I03 will move clockwise in Figure 3. During this movement the pawl MI is in engagement with the ratchet I I0 and will thereby prevent that ratchet and the gear I09 from rotating relative to the part I0 I. While the member I03 is moved clockwise, however, idlers I30 and gear I25 upon which the print wheel is mounted will rotate, thereby moving the print wheel clockwise in Figure 3 and counter-clockwise in Figure 2 to bring a new printing character into printing position above the chart drum. This indexing or movement of the printing character, which is next to be printed, into printing position takes place at that stage in the cycles of operations during which the pawl I4I locks the ink pad assembly against rotation relative to the print wheel carriage and immediately precedingv the downward movement of the print wheel which carries the selected printing character into engagement with the chart 2I9. As this clockwise movement of the part I03 continues the roller I39 will move away from the pivot point I42 and the lever arm between I39 and I42 will become large enough for Y spring I38 to overcome the force of spring I43. At this time the pawl I35 will move into engagement with the ratchet I I0 and maintain the parts in the position shown until the next printing operation occurs. It will be seen, therefore, that the ratchet H0 is positively locked for movement with the part I03 by pawl I" or is positively locked against movement by the pawl Ill. At no time is the ratchet wheel, and therefore the print wheel, free to rotate because the pawls are so designed that pawl MI is moved into engagement with a tooth of the ratchet as pawl I" is moving out of engagement therewith. It will, therefore, be seen that as channel I starts to move after the instrument has come into balance its movement will produce a printing operation and then an operation whereby a new printing character is brought into printing position above the chart.

From the above description it will be seen that I have provided a print wheel carriage mechanism which is simple and accurate. This carriage is characterized by the fact that the print wheel and the ink wheel are always moved a predetermined amount as a result of each printing operation. It will be seen that it is practically impossible for the parts to get out of step with each other.

While in accordance with the provisions of the statutes I have illustrated and described the best forms of the invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention as set forth in the appended claims, and that in some cases certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention what I claim as new and desire to secure by Letters Patent is as follows:

1. A multiple recording instrument comprising a print wheel carriage, a member mounted for pivotal movement on said carriage, means to move said member in opposite directions through a path, a print wheel having a plurality of printing characters rotatably mounted on said member, an ink pad wheel rotatable on said member whereby different characters on said print wheel may be brought into engagement with different portions of said ink pad wheel, a ratchet mounted to rotate with said ink pad wheel, a first pawl on said carriage biased to engage said ratchet, a second pawl on said carriage biased to engage said ratchet, cooperating means between said first and second pawls acting to keep one of said pawls out of engagement with said ratchet in each direction of movement of said member, whereby upon movement of said member in one direction said ratchet will move with said member and in movement of said member in the opposite direction said member will be rotated relative to said ratchet, and means to rotate said print wheel as said ink pad wheel rotates relative to said member.

2. In a multiple recording instrument, a print wheel carriage comprising a member pivoted thereon and adapted to be moved in opposite directions through a path, an ink pad assembly rotatably mounted on said carriage coaxial with said member, a ratchet rotatable with said assembly, a first pawl mounted on said member and biased toward engagement with said ratchet,

a roller extending from said pawl, a second pawl pivoted on said carriage and biased toward engagement with said ratchet and having an extension thereon upon which said roller bears, means to move said member in such a direction that said roller will move along said extension toward the pivot point of said second pawl said movement continuing until the leverage of said extension between said pivot point and roller is short enough for the bias of said second pawl to move said second pawl into engagement with said ratchet and move said first pawl out of eng'agement therewith, said moving means then moving said member in the opposite direction. said second pawl operating to hold said ratchet stationary as said member moves, a print wheel rotatably mounted on said member, and gearing between said ratchet and print wheel.

3. In a multiple recording instrument, a print wheel carriage, a member mounted for oscillation on said carriage, an ink wheel assembly mounted for rotation on said carriage coaxial with said member, a print wheel having a plurality of printing characters thereon cooperating with said ink wheel and mounted for rotation on said member, gearing between said print wheel and ink wheel assembly whereby rotation of one produces rotation of the other, a ratchet wheel attached to said ink wheel assembly, pawls on said member and on said carriage biased respectively toward engagement with said ratchet wheel, cooperating means between said pawls whereby one of said pawls is at all times in engagement with said ratchet, and means to move said member relative to said carriage.

4. In a multiple recording instrument, a print wheel carriage, a print wheel having a plurality of print characters rotatably supported on said carriage, an ink wheel having mounted thereon a plurality of ink pads, one for each printing character, said ink wheel comprising a tubular body having an inwardly extending flange on one end, said flange having an opening therein a portion of which is concentric and a portion of which is eccentric to said ink wheel, means to support said ink wheel comprising a shaft having a shoulder concentric therewith to receive the opening in said flange, said opening permitting the ink wheel to be moved laterally of said shaft so that the ink pads will be out of engagement with the printing characters as the ink wheel is being mounted on said shaft, and a part received by said shaft being provided with a concentric shoulder adapted to fit into the end of said tubular body to normally center the same on said shaft.

5. In a multiple recording instrument, the combination of a print wheel carriage, a print wheel having a plurality of printing characters therein mounted for rotation on said carriage, an ink wheel assembly having a plurality of ink pads, one for each printing character, also mounted for rotation on said carriage, said assembly including a tubular body having a plurality of radial flanges extending outwardly and along the length thereof between each pair of which an ink pad is located, said body also having an inwardly extending flange through which is an opening a portion of which is concentric and a portion of which is eccentric to said member, and a notch at the edge of the opening adjoining said portions, means to mount rotatably said assembly on said carriage including shaft extending through the opening of said tubular body and having a pin adapted to be received by said notch, said pin and notch serving as a pivot for said assembly whereby it may be moved to separate the ink pads from the print wheel as the assembly is being placed on its supporting shaft, and means to center and hold said assembly in position.

6. In a multiple recording instrument, a print wheel carriage, a member mounted for oscillation on said carriage, an ink wheel assembly mounted for rotation on said carriage coaxial with said member, a print wheel having a plurality of printing characters thereon, said print wheel being mounted on said member in a position so that the printing characters engage with the ink wheel. gearing between said print wheel and ink wheel whereby rotation of one produces rotation of the other, a ratchet wheel having an extending shaft upon which said ink wheel is mounted, pawls on said member and carriage biased toward engagement with said ratchet wheel, cooperating means between said pawls whereby one of said pawls is at all times in engagement with said ratchet, means to move said member relative to said carriage, said ink wheel having a tubular body having an inwardly extending flange on one end, said flange having an opening therein, a portion of 10 which is concentric and a portion of which is eccentric to the tubular body and a notch at the edge 0! the opening adjoining said portions, a pin on said ratchet and extending parallel to said shaft and adapted to be received by said notch, said pin and notch serving as a pivot for said tubular member whereby the latter may be rotated about the pivot so that the shaft is received by said eccentric portion as said ink wheel assembly is being moved into place to separate the ink wheel from the print wheel, and means to center and hold said ink wheel assembly in place on said shaft.

JOHN A. CALDWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,085,325 Miller June 29, 1937 2,207,343 Fairchild July 9, 1940 2,328,664 Moore Sept. 7, 1943 

